Human beings are really advanced neural networks, trained on years of sensory data, along with lots of bias factors. This is why things like sexism and racism are often self-perpetuating. People aren't used to commonly seeing a female, minority woman in a high position, so they don't expect it, and therefore that expectation becomes part of their bias in the future.
There are only two solutions:
(1) Do things to create more minority female tech executives, so we all expect it.
(2) Do things to make people better at hiding their biases.
Obviously, we need to do both if this situation is ever going to change.